Most soldering paste fluxes currently in use are petrolatum-based and usually contain zinc and ammonium chloride. The use of petrolatum is disadvantageous because petrolatum is not water soluble and leaves a greasy residue behind. Further, in a typical solder paste flux formulation, the residue contains zinc and ammonium chloride which is corrosive to copper pipe.
There are a relatively large number of patents in the broad field of soldering fluxes, and some of these patents are discussed below.
U.S. Pat. No. 4,895,606 to Jafri discloses a soldering flux composition comprising a water soluble oil-in-water emulsion paste comprised of an oil type material (such as, e.g., petrolatum), an emulsifier such as glyceryl monostearate and alcohol, a substantial amount of water and a fluxing agent.
U.S. Pat. No. 3,796,610 to Sarnacki et al discloses water soluble soldering fluxes used in soldering electrical surface soldering connections and printed circuits. The fluxes principally comprise glycerol (80% to 90%) and include hydrochloric acid and tartaric acid.
U.S. Pat. No. 3,436,278 to Poliak discloses glycol soldering fluxes used in soldering electrical connections. The fluxes are generally comprised of glutamic acid hydrochloride polyglycols and alkyl alcohols.
U.S. Pat. No. 4,872,928 to Jacobs discloses a water-soluble paste for electronic circuits consisting essentially of a solder powder (e.g., a Sn/Pb alloy), a water-soluble organic activator (e.g., a mixture of 2-ethyl hexyl amine hydrobromide, triethanolamine and citric acid) and a polyethylene vehicle.
U.S. Pat. No. 5,215,602 to Ali et al discloses a water-soluble flux for printed circuit boards including a vehicle including at least two random copolymers of polyalkylene glycol with various amounts of ethylene oxide and propylene oxide. The flux includes a relatively large amount of water as well as a number of other constituents including hydrobromic acid.
U.S. Pat. No. 3,220,892 to Durham discloses soldering fluxes adapted for use in soldering copper and copper-based alloys wherein the fluxes consist essentially of a water solution of a water-soluble salt of an acid of a particular character. A relatively large number of acids are mentioned including hydrobromic acid.
U.S. Pat. No. 2,978,360 to Battle et al discloses soldering fluxes which are said to be substantially residue-free and which consist essentially of ammonium halides and substituted ammonium halides, and hydrogen bromide as uncombined hydrobromic acid.
U.S. Pat. No. 2,880,126 to Jordan et al discloses soldering fluxes for the joining and the coating of metals which include, inter alia, a large percentage (preferably 80 to 90%) of amine hydrohalide or combination of hydrohalides.
U.S. Pat. No. 5,443,660 to Gao et al, discloses a water-based, “no-clean” flux formulation for electronic and circuit boards comprising a solvent, a water soluble weak organic acid, a halide-free, non-ionic surfactant (such as, e.g., Tergitol TMN-6), and a biocidal co-solvent.
U.S. Pat. No. 3,902,928 to Yen et al discloses a metal joining flux wherein the active fluxing ingredients are cupric chloride and zinc chloride. Wetting agents such as Tergitol may be added to the active fluxing ingredients.
U.S. Pat. Nos. 2,895,862 and 3,099,590, both to Laudenslager, Jr., disclose solder fluxes for soft solders and the like wherein the fluxes include, inter alia, a small amount of a wetting agent such as, among others, Tergitol EH, Tergitol XD and Tergitol #4.